Lockstitch shoe sewing machines



Nov. 15, 1955 N. v. GERMANY 2,723,634

LOCKSTITCH SHOE SEWING MACHINES Filed Feb. 25, 1954 s Sheets-Sheet i Elia (Ji n Inventor Norman V Germany Nov. 15, 1955 N. v. GERMANY 2,723,634

LOCKSTITCH SHOE SEWING MACHINES Filed Feb. 25, 1954 6 Sheets-Sheet 2 [nuen far Norman l ermany Nov. 15, 1955 N. v. GERMANY LOCKSTITCH SHOE SEWING MACHINES 6 Sheets-Sheet 3 Filed Feb. 25, 1954 [nuen for Normal? V619 rmany Nov. 15, 1955 N. v. GERMANY 2,723,634

LOCKSTITCH SHOE SEWING MACHINES Filed Feb. 25, 1954 6 Sheets-Sheet 4 Nov. 15, 1955 N. v. GERMANY 2,723,634

LOCKSTITCH SHOE SEWING MACHINES Filed Feb. 25, 1954 6 Sheets-Sheet 5 v I z 1955 N. v. GERMANY 2,723,634

LOCKSTITCH SHOE SEWING MACHINES Filed Feb. 25, 1954 6 Sheets-Sheet 6 W W T 7 D X p 592 [17 uemor N rman V66)" man y ilnited States LOCKSTITCH SHOE SEWING MACHINES Norman Victor Germany, Leicester, England, assignor to United Shoe Machinery Corporation, Flemington, N. J., a corporation of New Jersey Application February 25, 1954, Serial No. 412,564 Claims priority, application Great Britain May 6, 1953 Claims. (Ci. 112-47) The present invention relates to shoe outsole lockstitch sewing machines of the type disclosed in United States Letters Patent No. 1,169,909, granted February 1, 1916, upon application of Fred Ashworth, and more particularly to improvements for the purpose of rendering the machine of that patent capable of operating at higher speeds than heretofore while maintaining a desirable relatively simple construction without detracting in any way from the effectiveness of operation and the high quality of work obtainable.

The desirability of a moving work clamp as distinguished from a laterally shifting awl to feed a shoe being operated upon in a high speed shoe outsole sewing machine has been recognized for a number of years. Such clamp is preferred for accurate location of stitches both by reason of its greater rigidity as compared to a work feeding awl and for the reason that it may be engaged with a shoe for a longer period of time in each sewing cycle than is possible with an awl, the awl being engaged with the work and retracted promptly to admit the sewing needle into the perforation formed thereby before each stitch is completed. Thus, with a work feeding clamp 21 greater length of time may be allotted in each sewing cycle to work feed than with an awl feed machine. Accordingly, the rate of acceleration and deceleration in the feeding movement imparted to work being sewn may be made much lower with a clamp feed machine than with an awl feed machine, and consequently there is less stress on the machine and the work, which includes ashoe and a relatively heavy last therein.

Prior shoe outsole sewing machines of the clamp feed type, such as disclosed in United States Letters Patent No. 2,056,670, granted October 6, 1936, upon application of Gouldbourn et al., and No. 2,271,611, granted February 3, 1942 on application of Ashworth et al., have their work feeding clamps mounted on carriers to swing through arcuate paths about fixed pivots. To reduce vibration in a work feeding clamp carrier it is made to swing through an arcuate path of relatively large radius, reducing to a minimum the amount of forward and rearward movement of the feeding clamp, which forward and rearward movement is the greatest vibration producing factor and the greatest cause of discomfort to an operator presenting a shoe to the machine. However, a carrier swinging through a path of relatively large radius necessarily has a long supporting arm which causes an undesirable reaction from flexibility inthe arm and lost motion in its supporting bearings, so that irregular feeding movements of the clamp may occur after considerable wear in a machine of this construction.

An object of the present invention is to provide a comparatively rigid work feed which is free from lost motion in a sewing machine of the type disclosed in the patents referred to, by employing a work feeding clamp which moves in a straight line rather than in an arcuate path, the feeding clamp being applied to the machine in place of the awl feed of the machine disclosed in Patent No. 1,169,909 and requiring a relatively small number of replacement parts to make the change. A further object is to improve the operation of a shoe outsole sewing machine similar to that disclosed in Patent No. 1,169,909, so that it will operate effectively when stitches are inserted at a rate of speed corresponding to that at which the machines of Patents Nos. 2,056,670 and 2,271,611 are capable of operating, both the work and the sewing thread being handled by improved mechanisms co-operating to eliminate difficulties commonly met heretofore in attempts to sew at a. more rapid rate than usual with the machine of Patent No. 1,169,909.

With these and other objects in view the illustrated machine is a curved hook needle shoe outsole sewing machine having a work support and a presser foot forming a work gripping clamp which is moved in the direction of work feed along rectilinear guides mounted so close to the front portions of the machine frame that the remaining structure in the machine requires no other change and operates in substantially the same manner as in the prior patented machine, the needle and presser foot, looper, take-up and other stitch forming devices being actuated by the same mechanisms heretofore employed and the work feeding movement being imparted to the clamp comprising a presser foot guided on the machine frame independently of the work support but moved in the direction of feed by the same mechanism heretofore employed, except for the substitution of a new feed cam allowing a relatively longer time to feed the work.

These and other features of the invention as hereinafter described and claimedwill readily be apparent from a consideration of the following detailed specification taken in connection with accompanying drawings, in which:

Fig. 1 is a perspective view looking from the left front upper part of a machine embodying the features of the present invention;

Fig. 2 is a view in right hand side elevation with some of the parts broken away, showing the mechanism for actuating the presser foot toward: and from clamping engagement with the work;

Fig. 3 is a planview looking in. the direction of the arrow in Fig. 2 and showing parts of the work feeding mechanism;

Fig. 4 is a view in front elevation on an enlarged scale, partly insection of the structure for supporting the needle, awl, work support and presser foot with some parts broken away;

Fig. 5 is a view inv left hand side elevation, partly in section and partly broken away, of the structure illustrated in Fig. 4;

Fig. 6 is a. detailed view in left side elevation and partly in section of a thread lock mechanism employed inthe machine;

Fig. 7 is a sectional view of the parts illustrated in Fig. 6 looking, in the direction of the arrow in that figure;

Fig. 8 is a time chart showing successive positions of certain devices during. each stitch forming cycle of the machine; and

Fig. 9 is a separated perspective detail view showing the construction of a front thread lock in the machine.

The illustrated machine is generally similar to the shoe outsole lockstitch sewing machine disclosed in United States Letters Patent No. 1,129,760, granted February 23, 1915, upon application of L. E. Topham, No. 1,169,909 above-identified, No. 1,233,539, granted. July 17, 1917, upon application of Fred Ashworth, and No. 1,519,652, granted December 16, 1924, upon application of Fred Ashworth. Reference may be had to those patents for a better understanding of the present invention.

The machine has a main frame: 2 which is substantially the same as that disclosed in the patents referred to. Mounted on forwardly projecting lug portions 4 of the main frame by screws 6 and dowel pins 8 are a pair of side arms 10 and 11 having bearings for a needle and awl supporting stud 12. The machine is improved by providing a relatively simple set of attachments for a clamp feed mechanism, comprising carriers for a work support and presser foot and for an improved thread lock mechanism, as will be more fully described, actuated from a main sewing shaft 14 (see Fig. 6), which differs from the shaft referred to as 11 in Patent No. 1,169,909 only in having keyed to it an additional eccentric 16 for actuating the thread lock.

Mounted on the needle and awl stud 12 of the illustrated machine is a needle segment 18 (see Figs. 4 and to which is clamped at the presser foot side of the work a curved hook needle 20 and an awl segment 22, to which is clamped at the work support side of the work a curved awl 24, the awl segment being formed integral with the stud 12. Other stitch forming devices include a loop taker 25 for passing a locking thread through each loop of thread drawn through the work by the needle, a take-up 26 and thread measuring mechanism comprising a needle thread pull-off 27. The stud 12 thus rotates with the movement of the awl as it is actuated toward and from engagement with the work, the ends of the stud being supported by bearings in the side arms. The stud 12 and the awl segment 22 differ from the parts referred to as 41 and 39 in Patent No. 1,169,909 only in that they are restrained from axial movement in the direction of work feed by an angle plate 28 adjustably attached to the left hand side plate and formed with a slotted flange entering a circumferential groove 29 in the stud 12, the flange on the angle plate fitting the groove in the stud to prevent axial movement. With this construction the awl segment is maintained in the same plane as the needle 20, axially of the stud. To insure accurate alinement between the needle and awl the plate 28 may be adjusted by loosening a clamp screw 30 which passes through a slot in the plate 28 and into threaded engagement with the arm 10. Adjusting movement of the plate 28 to the right or left as seen in Fig. 4 causes the stud 12 to move axially by reason of the groove and flange connection with the plate. To facilitate right or left adjusting movement of the plate 23 a second slot in its flange is engaged by an adjusting screw 31 threaded into a shoulder on the arm 10. The head of the adjusting screw 31 engages one side of the plate 28 and a collar on the screw engages the other side of the plate to cause movement of the plate to the right or left as the screw is rotated. After bringing the awl into alinement with the needle, the clamp screw 30 is tightened to secure the parts in adjusted relationship by forcing the angle plate against the side plate 10. The awl is actuated toward and from the work by mechanism similar to that in Patent No. 1,169,909 and in the same timed relationship with the operation of the other stitch forming devices.

With the use of a work feeding awl, such as that disclosed in Patent No. 1,169,909, the. work is securely clamped during formation of each stitch by a presser foot acting against a Work support rigidly mounted on the frame of the machine with no opportunity for flexure or shifting movement in the direction of feed and no problem of wear and looseness in the parts. During feed of the work it is guided by engagement with the work support so that there is no appreciable vertical displacement, the work being moved a stitch length during each sewing cycle by the awl which is projected through a slot in the work support. However, the awl is a somewhat flexible member and when subjected to severe stress in the direction of the work feed does not bring a heavy shoe and last instantly from one position into another position where a new stitch may be inserted, the awl tending to flex and impress a yielding accelerating force on the shoe. The shoe under the yielding force of the awl is gradually accelerated and then, without stopping when the accelerating force ends, is decelerated after the feeding movement of the awl is completed. If the presser foot acts to clamp the shoe before it has had an opportunity to rebound under the yielding decelerating force applied by the awl, it will be clamped at a position of overthrow where the perforation formed by the awl is beyond a position of alinement with the needle. The needle then will be required to form its own perforation in the work and a seam will be inserted which is objectionable because of so-called double holing. To avoid this objection it is common practice to locate the needle and awl somewhat out of alinement when no work is in the machine, so that overthrow in the movement of a shoe as a result of the yielding decelerating force of the awl will bring the awl perforation in a shoe exactly into line with the needle. However, this adjustment is effective to stop double holing only when the machine is running at its rated speed. When run at a slower speed or with an adjustment for shorter stitches where the acceleration and deceleration of the shoe from feeding movements of the awl are greatly reduced, the awl perforation again will reach a position of misalinement with the needle since the awl no longer applies such strong force to a shoe. Accordingly, the needle is still required under these conditions to form its own perforation again resulting in objectionable seams.

These difficulties, however, have been avoided heretofore by the use of a clamp feed mounting including a single movable carrier for both the work support and the presser foot and mechanism has been provided for actuating the parts to cause-the work support and presser foot to clamp and feed the work in proper timed relation to the functions of the needle and awl, the awl being maintained in continued alinement with the needle without imparting a feeding movement thereto. The usual practice has been to provide a work support and a presser foot mounted on a carrier which swings, its swinging axis being secured in fixed relation to the frame of the machine some distance behind the needle and awl stud and a pair of supporting side arms therefor. With the carrier extending from its axis of swinging movement forwardly through the required distance it does not possess the same rigidity as that obtained when a non-feeding presser foot and a non-feeding work support are fixed to the machine frame at a. position much closer to the point of operation of the needle and awl. Accordingly, additional guiding and bracing surfaces are required on the machine frame for the presser foot and work support carrier which render the construction in the machine more expensive and more susceptible to wear than otherwise. Also, it is common practice to provide a presser foot lever fulcrumed on the same carrier with the work support so that the work clamping and releasing movements of the presser foot toward and from the work support occasionally result in an additional series of undesirable vertical reactions in the carrier and in corresponding wear on the guiding and bracing surfaces. These reactions tend to cause the work clamping action of the presser foot actuating mechanism to be influenced irregularly with such construction to an objectionable degree.

To overcome the difficulties commonly met by the use of a clamp feed in which a work support and a presser foot are mounted for swinging movement on a single carrier, the swinging axis of which is located at a position a substantial distance at the rear of the needle or awl supporting stud in an outsole sewing machine, the illustrated work clamping and feeding attachment is so mounted that adequately rigid support is provided for the work support and presser foot while all the other desirable features of a clamp feed machine are retained. Furthermore, the improvements incorporated in the attachments render them readily applicable to the machine of Patent No. 1,169,909, merely by substitution of parts carried on mountings already existing in the machine of the patent without extensive machine work. For this purpose the side arms 10 and 11 differ from the arms 42 and 43 of Patent No. 1,169,909 in that they are provided with guides having surfaces directed in parallel relation to the needle and awl stud 12 and it's bearings. These guides consist of journal bearings 32 (see Fig. 5) in the side arms and 11 and a pin 34 clamped within laterally spaced lugs 36 and 38 (see Fig. 4) on the right side plate 11. For clamping the pin 34 and the right hand lug 36 has at its upper end a split socket across the split in which passes a clamp screw 40 (see Figs. 2 and 3) to draw the socket securely against the pin 34. To overcome the vertical reaction on the work support by reason of the clamping and releasing movements of the presser foot, the presser foot of the illustrated machine, indicated at 42, is secured by clamp screws 44 to a combined carrier and presser foot lever 46 fulcrumed for lateral sliding movement on the pin 34. This combined carrier and presser foot lever is made separate from a carrier 48 to which is clamped the work support, indicated at 50, and the presser foot carrier is isolated from the work support carrier against transmission of vertical work clamping movements of the presser foot to the work support.

The work support 50 is U-shaped looking from above and is secured to its carrier 48 at its ends. The carrier 4-8 is in the form of a bar having at its ends trunnions S2 of reduced diameter and between its ends is a pair of radially projecting lugs to which the ends of the work support are secured. The trunnions 52 are slidably mounted in the journal bearings 32 which are coaxial, one in the arm 10 and the other in the arm 11, the axis of the journal bearings 32 being located below and forwardly of the guide pin 34 for the presser foot and parallel therewith.

To retain the Work support securely in proper vertical position against rotation about the axis of the journal bearings 32, the work support carrier 48 has a rearwardly projecting arm carrying a tongue 54 formed with finished faces engaging a horizontal guideway 56 (see Fig. 5) cut in a block 58 bolted by screws 6 to the frame 2. The surfaces of the guideway in the block 58 are parallel to the axis of the journal bearings 32 to insure easy sliding movement of the work support carrier.

To isolate the work support carrier against transmission of vertical work clamping movements of the presser foot to the work support and, at the same time, to insure simultaneous work feeding movements of the work support and presser foot, the work support carrier 48 has a vertical slot 60 having finished internal parallel surfaces engaged with corresponding external surfaces on a tongue 62 carried by a downwardly projecting lug on the presser foot carrier 46. The presser foot carrier 46 has a bifurcated portion straddling the lug 38 on the side arm 11 with one portion engaging the guide pin 34 between the lugs 36 and 38 of the side arm 11. The arrangement is such that as the presser foot carrier 46 slides on the guide pin 34 the work support carrier 48 also slides in its guide journal bearings through the action of the tongue and slot connection 60, 62 (see Fig. 3), thus preventing independent feeding movements between the presser foot and work support.

To impart work feeding movements to the work clamp comprising the work support and presser foot, means are provided for shifting the presser foot carrier lever axially along the guide pin 34. For this purpose the hub of the carrier lever 46 is provided with two parallel slots 64, one in the upper portion of the hub and one in the lower portion thereof. Engaging the slots 64 in the hub of the presser foot carrier lever are enlarged flattened heads of two co-axial pivots 66 having reduced portions rotatably mounted, one in each branch of a forked feed lever 68'. The feed lever is fulcrumed on an inclined pivot 70 fixed in the machine frame 2. This pivot is one of a pair including a pivot 72 already in the machine and corresponds to the pivots on which the feed levers 44 and 45 of Patent No. 1,169,909 are mounted. A

rearward arm of the lever 68 is pivotally connected by '6 a link 74 to an intermediatev portion. of a. lever 76 fulcrumed on the inclined pivot 72. The rearward end of the lever 76 is connected to a toggle link 78 similar to the part referred to as 49 in Patent No. 1,169,909, and functions in the same manner to impart a Work feeding movement to the presser foot carrier lever. Since it is possible with the use of a work feeding clamp to increase the time allotted in a sewing cycle for the accomplishment of work feed over that employed in the awl feed machine of Patent No. 1,169,909, the feed cam which is mounted on the sewing shaft 14 differs from that in the patented machine in a manner more fully to be described.

To actuate the presser foot through its work clamping and releasing movements the presser foot carrier lever has at its rearward end a ball headed pin 80 (see Figs. 3 and 5) engaging a socket in the upper end' of a link 82 (see Fig. 2), and a socket in the lower end of the link 82 surrounds a ball end of a lever 84 fulcrumed on a pin 86 fixed to the right hand side arm 11. Rocking movement of the lever 84 raises and lowers the presser foot, the link 82 being relatively long compared with the feeding movement imparted to the presser foot carrier lever so that little or no movement is imparted to the presser foot toward and from work as a result of foreshortening movement of the link 32. To actuate the lever 84, a downwardly extending arm is pivotally connected to a link 88, and the link 88 is in turn similarly connected to a floating lever 90. This floating lever is similar in construction and in mode of operation to that referred to by the numeral 6 in Patent No. 1,169,909. Another point upon the floating lever 90 is pivotally connected to alock 92, and a third point at the upper end of the lever is pivotally connected to an actuating link 94 similarly connected to a lever 96 fulcrumed on a pin 98 secured in the machine frame and provided with a cam roll 100 actuated by a cam on the main sewing shaft 14.

To actuate the presser foot yieldingly against the work in clamping the work during eachsewing cycle the lower end of the" floating lever 90 isv connected through a link 102 with an arm 104' corresponding to the arm 163 in Patent No. 1,169,909, this arm being secured to a rockshaft rotatable in the machine frame. Also pivotally connected to the arm 104 is a forward end of a link 106 connected at its rearward end with a bell crank lever 108 rotatably mounted with a shaft 110 in the frame of the machine; The bell crank lever 108 has on its rearward arm a pin 112 projecting through the slot in the lower end of a slotted link 114, and the pin 112 has connected to it the upper end of a spring 116 which acts through the connections described above to force the presser foot yieldingly against the work.

To raise the presser foot from engagement with the work at the completion of a seam the slotted link 114 which remains idle during normal sewing operations is pivoted at its upper end to a lever 117 similar to the lever 3940 shown in Patent 1,233,539. Rocking movement of the lever 117 in one direction unlocks the presser foot in a manner similar to that described in Patent No. 1,233,539, and further rocking movement in the same direction brings the lower end of the slot in the link 1114 against the pin 112 to lift the presser foot from engagement with the work through the connections described. The lever 116 is operated automatically on stopping the machine to lift the presser foot, or if preferred the lever is connected through a link 118 to a hand lever 1211 rotatably mounted on the shaft 98 to produce the same result manually.

The timing of the movements of the needle, awl and clamp feed will now be described with reference to Fig. 8. In this figure measurements along the X or horizontal axis represent degrees of rotation of the main shaft 14 and measurements along: the Y or vertical axis indicate the movements of certain parts of the machine of during one stitch forming cycle. In the diagram a single rotation of the mainshaft 14 is represented as commencing 7 and finishing in the normal stopped position of the machine.

The line AA and the line B-B represent the successive positions of the points of the needle and awl, respectively, with regard to the work engaging surface of the work support, this surface being represented by the line TT, and the upper surface of a work piece of ordinary thickness being represented by the line WW.

The line CC represents successive positions of the feed clamp carriers 46 and 48 relative to the plane of the needle and awl.

Considering first the movements of the needle it is apparent from line AA that, at the start of the stitch forming cycle illustrated, the needle point is above the surface of the work support and rising. By the time the main shaft has turned through 60 the needle point is about to descend, afterwards entering the work, passing through a perforation made by the awl and reaching the surface of the work support when the main shaft has turned through about 104. The needle reaches its lowest position when the main shaft has turned through about 137, afterwards rising to withdraw from the work, reach ing its highest position after the main shaft has turned through about 240, and remaining above the work piece for the remainder of the stitch forming cycle. The angular positions of the main shaft at which the needle point enters into and Withdraws from the work piece are shown as about 98 and 184, respectively, but it will be clear that these positions will be somewhat different for a work piece which is either thicker or thinner than the work piece selected for purposes of illustration.

The point of the awl acts in the same circular path and plane as the point of the needle and remains always below the needle. The line B-B in Fig. 8 shows that at the start of the stitch-forming cycle, the awl point is rising up towards the surface TT of the work support. The awl point commences to pierce the work from the underside when the main shaft has turned through about 12. The awl point pierces the work and then withdraws as the main shaft turns through about 99. The needle point enters the upper face of the work piece before the awl is completely withdrawn. Having withdrawn, the awl point remains below the work piece for the remainder of the stitch-forming cycle.

The feed clamp carriers 46 and 48 are actuated by cam driven mechanism similar to that disclosed in the prior Ashworth patents for actuating the awl to feed the work. At the start of the stitch-forming cycle the feed clamp carriers are idle after completing a Work feeding movement, that is, the work support and presser foot remain stationary after completing a movement to the left. After the main shaft has turned through about 51, as will be seen from line CC in Fig. 8, the clamp carriers commence to back feed together toward the right, this back feed being complete when the main shaft has turned through about 90. During back feed it will be clear from an inspection of the line EB that the awl is holding the work piece in a stationary position. Having completed the back feed the work support and presser foot remain stationary until the main shaft has turned through about 210. The work support and presser foot then start to feed the work to the left, completing the work feeding movement when the main shaft has turned through about 360. It will be seen from an inspection of the lines AA and EB that the feeding movement of the clamp is spaced over almost all that part of the stitch forming cycle (150) in which both the awl and the needle are clear of the work piece, whereas, if the work were fed by the awl, the entire feed would be restricted to the time (70") in which the awl enters the work.

The presser foot lock is represented by the line DD and is locked at the commencement of the stitch-forming cycle. It is unlocked when the back feed of the clamp is complete, that is, when the main shaft has turned through about 90, in order that the presser foot may be 8 pressed down on the work by spring pressure. The presser foot lock is locked again when the main shaft has turned through about 106 and remains locked for the remainder of the stitch-forming cycle.

The presser foot clamping and releasing movements are shown in line EE. At the start of the stitch-forming cycle the presser foot is clamping the work. The presser foot starts to lift when the main shaft has turned through about 40 and by the time the main shaft has turnedthrough about 75 the presser foot has been lifted to its highest position, allowing the feed clamp to be back fed while the work piece is held by the awl. It will be seen from line CC that the clamp starts to back feed before the presser foot is fully lifted. The presser foot remains disengaged from the work piece until the presser foot lock is released. This occurs when the main shaft has turned through about whereupon the presser foot engages the work piece under the force of its spring. The presser foot remains engaged with the work piece under spring pressure until the presser foot lock is locked, the main shaft having turned through about 106. As soon as the presser foot lock is locked the presser foot is given a small positive downward movement by its cam, this work compressing movement being completed when the main shaft has turned through about 108, after which the work piece remains positively clamped by the presser foot for the remainder of the stitch making cycle.

The present machine is equipped with thread measuring mechanisms including a pull-off and front and rear thread locks, the pull-off and rear lock, not being shown. These mechanisms correspond to those shown in Patent No. 1,519,652. The rear thread lock engages the thread between a measuring device and a supply for the thread, allowing a measured amount of thread to be drawn from the supply and thereafter holding the measured thread against return movement toward the supply. Between the pull-off 27 and the take-up 26, the thread is engaged by a front thread lock corresponding to that indicated at 28 in Patent No. 1,519,652. The front and rear thread locks of the machine shown in Patent No. 1,519,652 are actuated by a single rocking lever which permits both thread locks to be opened momentarily as one thread lock is opening and the other lock closing. In order to avoid any possibility of thread movement through both thread locks while open, the present machine provides a mechanism for actuating the front thread lock which is independent of the mechanism for actuating the rear thread lock, the arrangement being such that neither thread lock is open during a normal sewing cycle unless the other is fully closed, the thread thus remaining under control of one or the other of the locks at all times.

Referring more particularly to Figs. 6, 7 and 9 of the drawings, the front thread lock comprises a stationary jaw 122 bolted to the machine frame 2 and provided with a guide eye 124 through which the thread passes. Cooperating with the stationary jaw 122 is a movable jaw 126 having a corrugated face and being mounted on a screw 128 fixed in a forwardly extending arm of a bell crank lever 130, the jaw 126 being free to rotate slightly about the screw 128. The lever 130 is fulcrumed on a pivot 132 supported in a block 134 secured to the machine frame 2. To apply a thread locking pressure to the jaw 126 an arm of the lever 130 extending to the left carries a pivot pin 136 to which the forward end of and 138 is pivoted. The rearward end of the rod 128 is loosely supported in a passage within an adjusting screw 140 threaded in a lug in a bracket 142 bolted to the machine frame 2. Surrounding the rod 138 between one end of the adjusting screw 140 and a collar 144 clamped to the rod is a compression spring 146 acting through the rod and bell crank 130 to cause the jaw 126 to grip the thread yieldingly.

To actuate the jaw 126 and release its yielding grip on the thread, the left arm of the bell crank lever 130 has a socket formed to receive a ball at the forward end of an adjustable link 148, the rearward end of which is slotted and has passing through it a pin 150 (see Fig. 6). The pin 150 also passes through a forked arm of a lever 152, the fork of which surrounds the link 148, has its arms disposed at right angles to each other and connected together by means of a shaft 154 rotatably mounted in a lug on the bracket 142. Pivotally connected to a downwardly projecting arm of the lever 152 is one end of an eccentric strap 156 surrounding the eccentric 16. The arrangement is such that the pin 150 in the lever 152 moves for the greater part of its travel freely in the slot of the link 148, the pin not reaching the forward end of the slot in its most forward position. During its rearward movement the pin 150 engages the rearward end of the slot and moves the link 148 sufficiently to open the front thread lock 124, 126.

At the start of the cycle the front thread lock 124, 126 is open, the rear thread lock being closed. After the main shaft has turned a few degrees the front lock commences to close and is fully closed by the time the main shaft 14 has turned about 40. The rear thread lock opens when the main shaft 4 has turned through about 50 to allow thread to be drawn from the supply for a succeeding stitch and closes when the main shaft has turned through about 268. The timed relationship between the movements of the rear thread lock and the needle is similar to that of the corresponding parts of the machine disclosed in Patent No. 1,519,652. Almost as soon as the rear thread lock is closed the front thread lock opens after the main shaft 4 has turned through about 280 and remains open for the remainder of the stitch forming cycle to allow the rear thread lock to grip the thread during the setting of the stitch.

When the machine is stopped the position of the main shaft 14 is such that the front thread lock 124, 126 is open, and mechanisms are provided for opening the rear thread lock which would normally be gripping the thread in this position of the main shaft, these mechanisms being similar to those which operate the rear thread lock, referred to as 30 in Patent No. 1,519,652.

The use of a thread measuring mechanism having independently actuated front and rear thread locks, the front one of which is eccentrically actuated enables full advantage to be taken of a rigid clamp feed in place of an awl feed mechanism. Both locks being actuated independently and never releasing the thread at the same time contribute to accurate measurement in the thread even at the high speeds of sewing and work feeding permitted by the improved clamp feed.

The nature and scope of the invention having been indicated and a particular embodiment having been described, what is claimed is:

l. A shoe sewing machine having a main frame, a sewing shaft in the frame, a work support, a presser foot movable toward and from the work support to clamp the work, stitch forming devices actuated by the sewing shaft, including at the presser foot side of the work, a curved hook needle and loop taker for passing a locking thread through each loop of needle thread and at the work support side of the work, a take-up and a needle thread pull-off, a stud on which the needle is mounted for oscillation, and a pair of arms removably mounted on the machine frame and provided with bearings for the needle stud and with guides having surfaces directed in parallel relation to the needle stud, in combination with a carrier on which the presser foot is mounted movable along one of the said guides, and means for shifting the carrier along said one guide to impart a feeding movement to the presser foot.

2. A shoe sewing machine having a main frame, a sewing shaft in the frame, a work support, a presser foot movable toward and from the work support to clamp the work, stitch forming devices actuated by the sewing shaft, including at the presser foot side of the work a curved hook needle and loop taker for passing a locking thread through each loop of needle thread and at the work support side of the work, a take-up and a needle thread pull-off, a stud on which the needle is mounted for oscillation, and a pair of arms removably mounted on the machine frame and provided with bearings for the needle stud and'with guides having surfaces directed in parallel relation to the needle stud, in combination with a carrier on which the presser foot is mounted, movable along one of the said guides, means for shifting the carrier along said one guide to impart a feeding movement to the presser foot, a second carrier to which the work support is secured slidable on others of said guides in the removable arms, and connections between the presser foot carrier and the work support carrier to cause the two to move in the direction of work feed simultaneously.

3. A shoe sewing machine having a main frame, a sewing shaft in the frame, a work support, a presser foot movable toward and from the work support to clamp the work, stitch forming devices actuated by the sewing shaft, including at the presser foot side of the work a curved hook needle and loop taker for passing a locking thread through each loop of needle thread and at the work support side pf the work, a take-up and a needle thread pull-off, a stud on which the needle is mounted for oscillation, and a pair of arms removably mounted on the machine frame and provided with bearings for the needle stud and with guides having surfaces directed in parallel relation to the needle stud, in combination with a carrier on which the work support is mounted, movable along one of the said guides, and a carrier lever to which the presser foot is secured rotatably and slidably mounted on another of said guides.

4. A shoe sewing machine having a main frame, a sewing shaft in the frame, a work support, a presser foot movable toward and from the work support to clamp the work, stitch forming devices actuated by the sewing shaft, including at the presser foot side of the work a curved hook needle and loop taker for passing a locking thread through each loop of needle thread and at the work support side of the work, a take-up and a needle thread pull-off, a stud on which the needle is mounted for oscillation, and a pair of arms removably mounted on the machine frame and provided with bearings for the needle stud and with guides having surfaces directed in parallel relation to the needle stud, in combination with a carrier on which the presser foot is mounted movable along one of the said guides, a carrier lever to which the presser foot is secured rotatably and slidably mounted on one of said guides, a second carrier to which the work support is secured slidable on others of said guides, and tongue and groove connections between the presser foot carrier lever and the work support carrier to enable the presser foot carrier lever to be oscillated and the presser foot carrier lever and the work support carrier to be moved in the direction of work feed simultaneously.

5. A shoe sewing machine having a main frame, a sewing shaft in the frame, a work support, a presser foot movable toward and from the Work support to clamp the work, stitch forming devices actuated by the sewing shaft, including at the presser foot side of the work a curved hook needle and loop taker for passing a locking thread through each loop of needle thread and at the work support side of the work, a take-up and a needle thread pull-off, a stud on which the needle is mounted for oscillation, and a pair of arms removably mounted on the machine frame and provided with bearings for the needle stud and with guides having surfaces directed in parallel relation to the needle stud, in combination with a carrier on which the presser foot is mounted movable along one of the said guides, means for shifting the carrier along said one guide to impart a feeding movement to the presser foot, and a thread measuring mechanism including a pull-01f and a front thread lock References Cited in the file of this patent UNITED STATES PATENTS 1,169,909 Ashworth Feb. 1, 1916 12 Schoenky V Dec. 19, 1916 Ashworth etral. Feb. 3, 1942 Ashworth et a1 Apr. 2, 1946 

